The role of temperature in the solvothermal synthesis of hybrid vanadium oxyfluorides

The solvothermal synthesis of a new series of organically templated vanadium oxyfluorides is presented. The materials were synthesised from identical starting mixtures using temperature as the only independent variable. This shows a trend towards increasing dimensionality and decreasing vanadium oxidation state as a function of temperature. The materials were synthesised from a system containing V2O5-HF-H2O-ethylene glycol-piperazine which resulted in four new structure types, together with a previously known phase. [C4N2H12](3)[V2O2F8][VOF4(H2O)](2) (1) consists of V-(V)-centred monomeric units and V-(IV) edge-sharing dimers, which are held together by hydrogen bonding to form infinite chains. [C4N2H12](4)[V4O3F17].4H(2)O (2) features a Y-shaped tetramer containing both V-(III) and V-(IV)- centred octahedra which are held together via hydrogen bonding from the water molecules to form infinite sheets. [C4N2H12](4)[V5O3F20].2H(2)O (3) is a complex chain containing five different V-centred octahedra, which shares structural similarities with compound (2). The inter-relations between these three structure types as a function of temperature, together with two further compounds isolated from this system, are discussed.